1. Field of the Invention
This invention relates to a programmable battery controller and more particularly to a programmable apparatus, system and method for more accurately controlling and/or monitoring battery charge. The programmable battery controller includes a rechargeable battery, a host system microprocessor, a microcontroller, a charge gauge integrated circuit, and a display, which are programmed to allow a portable computer user to set battery monitoring parameters.
2. Background of the Relevant Art
Battery monitoring systems are commonly used to notify a portable computer user when a rechargeable battery needs recharging. Conventional battery monitoring systems often implement a software program that relies on a computer's hardware configuration and the power needed to run the components and peripherals. The software then monitors the usage of the components and peripherals to approximate the battery's drain rate and the remaining charge on the battery.
Such software approximates the remaining battery charge based on the power specifications of components and peripherals. Based upon power specifications for particular components and the chosen battery discharge rate, the software then calculates approximately where the battery's charge level currently resides. Such approximations fail to take into account the variances of actual components. In addition, the computer user must adapt the software whenever a portable computer is reconfigured with different parts or new batteries. Software programs necessary to achieve many of these functions are often referred to as terminate and stay resident (TSR) programs. TSR programs typically require multiple host computer interface operations which can, and often do, cause the host computer to lock up periodically or cause the program not to be run.
In an effort to overcome deficiencies of software approximation programs, more recent developments in charge monitoring devices have taken place. One such device monitors the voltage level of the rechargeable battery. An analog-to-digital converter may be employed to monitor the battery voltage throughout its operation. However, when a battery discharges during use, the voltage output generally reacts non-linearly. The non-linear discharge in the battery voltage may create false signals that a battery needs recharging when the battery, in fact, still contains sufficient charge. Alternatively, nonlinear discharge shows the battery as completely discharged even though adequate charge still remains. The false signals are read by the analog-to-digital converter which then outputs incorrect signals to the controller, and the controller prematurely charges the battery, thereby lessening the battery's capacity and lifetime.
Typical battery voltage monitors often cannot and do not indicate when a full discharge has occurred and that recharge is now needed to maintain optimal battery performance. Nickel cadmium batteries are commonly used in portable computers. However, nickel cadmium batteries are susceptible to the memory effect--they might not recharge fully if they're not first completely discharged. For example, if a battery is repeatedly recharged before reaching a low battery level, a three-hour battery may only last for one hour. A full battery discharge helps eliminate the memory effect. Conventional charge monitoring devices often do not store non-linear discharge information. As a result the computer user must know of battery characteristics, and monitor battery usage to determine when a discharge is necessary and how long discharge is needed in order to prolong battery life.
Some conventional monitoring devices use discrete components to measure the actual current drain on a battery. However such systems are bulky, do not provide flexibility, and do not exhibit accuracy. Battery discharge rates vary according to the batteries chemical composition, temperature, storage time, age of the battery, and load. Computer users find desirable battery monitoring systems which are not bulky and which can (i) determine when a discharge cycle is needed, (ii) determine an optimal discharge period, and (iii) perform the discharge and recharge cycles automatically under varying loads and operating temperatures.
Other conventional monitoring devices place significant portions of the monitoring circuitry external to the battery operated device. The battery operated device stores battery status data until an external circuit is connected and evaluates the battery's status. Unfortunately such systems do not provide real time battery status updates. Connections must occur before battery status can be read. Further, such systems require a user of a portable device to carry with him or her additional hardware circuitry and to connect that circuitry periodically to the battery operating device. Such constraints are cumbersome and make battery management and evaluation difficult.